net: dsa: b53: Prevent tagged VLAN on port 7 for 7278

On 7278, port 7 of the switch connects to the ASP UniMAC which is not
capable of processing VLAN tagged frames. We can still allow the port to
be part of a VLAN entry, and we may want it to be untagged on egress on
that VLAN because of that limitation.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_common.c

@@ -1355,6 +1355,14 @@ int b53_vlan_prepare(struct dsa_switch *ds, int port,
 	if ((is5325(dev) || is5365(dev)) && vlan->vid_begin == 0)
 		return -EOPNOTSUPP;
 
+	/* Port 7 on 7278 connects to the ASP's UniMAC which is not capable of
+	 * receiving VLAN tagged frames at all, we can still allow the port to
+	 * be configured for egress untagged.
+	 */
+	if (dev->chip_id == BCM7278_DEVICE_ID && port == 7 &&
+	    !(vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED))
+		return -EINVAL;
+
 	if (vlan->vid_end > dev->num_vlans)
 		return -ERANGE;